Systems are known whereby when a vehicle equipped with an onboard unit passes through a tollgate, a roadside antenna device provided at the tollgate and the onboard unit communicate via dedicated short-range communication (DSRC), and, on the basis of the communication result, a toll amount is determined. In such a system, when a communication result from communication between the roadside antenna device and the onboard unit cannot be obtained, it is determined that the cause may be that the onboard unit has been disconnected from the vehicle, and an image of the vehicle equipped with the onboard unit is transmitted to a data center. From this image, the toll infringing vehicle can be caught.
An onboard unit is known with an object of preventing theft and fraudulent exchange of onboard units. When the onboard unit detects that the onboard unit is disconnected from the vehicle, information on the detection is stored in memory. When wireless communication between the onboard unit and the roadside antenna is established, information on the detection of the attachment/removal of the onboard unit is read from the memory and transmitted (see Patent Document 1, for example).
Another known onboard unit with an object of preventing switching between vehicles, does not allow transmission of information outside the vehicle when the onboard unit is detected to have been removed from the inside of the vehicle, and controls the charge processing on the basis of the communication result with the roadside antenna (see Patent Document 2, for example).